tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1/*
2 * Copyright (C) 2001 Sistina Software (UK) Limited
3 *
4 * This file is released under the GPL.
5 */
6
7#include "dm-core.h"
8
9#include <linux/module.h>
10#include <linux/init.h>
11#include <linux/kmod.h>
12#include <linux/bio.h>
13
14#define DM_MSG_PREFIX "target"
15
16static LIST_HEAD(_targets);
17static DECLARE_RWSEM(_lock);
18
19#define DM_MOD_NAME_SIZE 32
20
21static inline struct target_type *__find_target_type(const char *name)
22{
23 struct target_type *tt;
24
25 list_for_each_entry(tt, &_targets, list)
26 if (!strcmp(name, tt->name))
27 return tt;
28
29 return NULL;
30}
31
32static struct target_type *get_target_type(const char *name)
33{
34 struct target_type *tt;
35
36 down_read(&_lock);
37
38 tt = __find_target_type(name);
39 if (tt && !try_module_get(tt->module))
40 tt = NULL;
41
42 up_read(&_lock);
43 return tt;
44}
45
46static void load_module(const char *name)
47{
48 request_module("dm-%s", name);
49}
50
51struct target_type *dm_get_target_type(const char *name)
52{
53 struct target_type *tt = get_target_type(name);
54
55 if (!tt) {
56 load_module(name);
57 tt = get_target_type(name);
58 }
59
60 return tt;
61}
62
63void dm_put_target_type(struct target_type *tt)
64{
65 down_read(&_lock);
66 module_put(tt->module);
67 up_read(&_lock);
68}
69
70int dm_target_iterate(void (*iter_func)(struct target_type *tt,
71 void *param), void *param)
72{
73 struct target_type *tt;
74
75 down_read(&_lock);
76 list_for_each_entry(tt, &_targets, list)
77 iter_func(tt, param);
78 up_read(&_lock);
79
80 return 0;
81}
82
83int dm_register_target(struct target_type *tt)
84{
85 int rv = 0;
86
87 down_write(&_lock);
88 if (__find_target_type(tt->name))
89 rv = -EEXIST;
90 else
91 list_add(&tt->list, &_targets);
92
93 up_write(&_lock);
94 return rv;
95}
96
97void dm_unregister_target(struct target_type *tt)
98{
99 down_write(&_lock);
100 if (!__find_target_type(tt->name)) {
101 DMCRIT("Unregistering unrecognised target: %s", tt->name);
102 BUG();
103 }
104
105 list_del(&tt->list);
106
107 up_write(&_lock);
108}
109
110/*
111 * io-err: always fails an io, useful for bringing
112 * up LVs that have holes in them.
113 */
114static int io_err_ctr(struct dm_target *tt, unsigned int argc, char **args)
115{
116 /*
117 * Return error for discards instead of -EOPNOTSUPP
118 */
119 tt->num_discard_bios = 1;
120
121 return 0;
122}
123
124static void io_err_dtr(struct dm_target *tt)
125{
126 /* empty */
127}
128
129static int io_err_map(struct dm_target *tt, struct bio *bio)
130{
131 return DM_MAPIO_KILL;
132}
133
134static int io_err_clone_and_map_rq(struct dm_target *ti, struct request *rq,
135 union map_info *map_context,
136 struct request **clone)
137{
138 return DM_MAPIO_KILL;
139}
140
141static void io_err_release_clone_rq(struct request *clone)
142{
143}
144
145static long io_err_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
146 long nr_pages, void **kaddr, pfn_t *pfn)
147{
148 return -EIO;
149}
150
151static struct target_type error_target = {
152 .name = "error",
153 .version = {1, 5, 0},
154 .features = DM_TARGET_WILDCARD,
155 .ctr = io_err_ctr,
156 .dtr = io_err_dtr,
157 .map = io_err_map,
158 .clone_and_map_rq = io_err_clone_and_map_rq,
159 .release_clone_rq = io_err_release_clone_rq,
160 .direct_access = io_err_dax_direct_access,
161};
162
163int __init dm_target_init(void)
164{
165 return dm_register_target(&error_target);
166}
167
168void dm_target_exit(void)
169{
170 dm_unregister_target(&error_target);
171}
172
173EXPORT_SYMBOL(dm_register_target);
174EXPORT_SYMBOL(dm_unregister_target);